Frames cost a lot of money, especially when you have to have a custom sized frame made for an odd-shaped painting. This is why most of my paintings remain unframed. Consequently, I’ve stored a lot of them by simply stacking them against one another.
This raises a problem with oil paintings, because for some reason they seem to retain a certain tackiness — at least mine seem to have done so. Consequently, the oil paintings I did on canvas paper, which is essentially a coated paper with a canvas texture, haven’t fared so well. One of them in particular (which I painted for our kitchen but never got around to framing) I found to be completely ruined when pulling it out recently. Parts of the painting’s surface had stuck to the boards against which it rested and pulled away from the paper stock, which ripped large chunks from the painting. So now, maybe, some day, I’ll get around to recreating this painting… But I doubt it.
The lesson to be learned is, carefully store your art so that this doesn’t happen to you.